Bioaccumulation Of Environmental Heavy Metals In Tree Sparrow Via Food And Its Exposure Risk Assessment

Heavy metals would be introduced into soil,water and atmosphere via industry,agriculture and people's daily life,influencing animals and plants in such polluted environment in varied degrees.Birds,an important part of ecosystem,are vital to maintain the balance of ecosystem.However,environmental heavy metals could enter and accumulate in different parts of birds via soil,water and food.Excessive heavy metals will bring some adverse effects to birds,including limitations of their growth,development,reproduction or even survival.Herein,in order to provide suggestions for establishing thresholds of heavy metal exposure risks to birds,tree sparrow?Passer montanus?,a passerine widely spread over Eurasia,was chosen as study object in the present study and Liangzhuang village in Baiyin district?BY,a mineral resources depleted city in China?was chosen as the heavy metal polluted sample area,Weichuan village in Liujiaxia district?LJX,a relative unpolluted scenic spot in China?as the control,to investigate copper?Cu?,zinc?Zn?,lead?Pb?and cadmium?Cd?accumulations in tree sparrow adults and their exposure risks to tree sparrow nestlings,juveniles and adults.The main results are shown as follows:1.Heavy metal concentrations in soils and waters of LJX and BY.Heavy metal concentrations in soils and waters in two areas were determined because heavy metals can be consumed by birds via soils and waters.Concentrations of Cd in soils from BY surpassed the threshold of environmental quality standards for soils?GB 15618-1995?and brought a moderate pollution,while Cu,Zn and Pb concentrations in soils from BY were below the thresholds.Lead and Cd concentrations in water from BY surpassed the thresholds of standards for drinking water?GB 5749-2006?while Cu and Zn concentrations were below the thresholds.Heavy metal concentrations in both soils and water from LJX were below the thresholds.Higher heavy metal concentrations were found in soils and water from BY compared to those from LJX?p<0.01?,indicating LJX can be a control sample area.2.Body parameters of tree sparrow juveniles and adults from both LJX and BY.For juveniles and adults,there was no significant difference between their body weights,body lengths,tail lengths,wing lengths,tarsus lengths and beak lengths of tree sparrows from LJX and BY?p>0.05?,indicating there is no significant effect of heavy metal pollution on body parameters of tree sparrow juveniles and adults from BY.3.Heavy metal concentrations in different parts and faeces of tree sparrow adults from LJX and BY.High heavy metal concentrations were found in primary feather,tail feather,breast feather and back feather of tree sparrow adult.Zinc and Pb were found in tarsometatarsu with high concentrations.High heavy metal concentrations were found in liver,kidney and faece,while low concentrations were found in muscle and blood.Heavy metal concentrations in primary feather,blood and faece of tree sparrow adult from BY were higher than those from LJX?p<0.05?,so they can be indicators of heavy metal pollution.4.Diet compositions of tree sparrow nestlings,juveniles and adults.SIAR was employed to investigate diet compositions of tree sparrows from both LJX and BY.For nestlings,non-phytophagous invertebrates?nph-in?had the biggest contribution to diet compositions,while maize and C4 plants belonging to Gramineae?C4-Gra?contributed lowest.With few exceptions,maize had the biggest contribution to diet compositions of juveniles and adults.All in all,tree sparrow nestlings from both LJX and BY consumed animal food most,while juveniles and adults consumed plant food most.5.Heavy metal concentrations in food of tree sparrows from both LJX and BY.Highest heavy metal concentrations were found in nph-in among different food sources,while the lowest were found in maize.With few exceptions,food sources from BY were found with higher heavy metal concentrations than those from LJX?p<0.05?.Food of nestlings had the highest average heavy metal concentrations?AC values?followed by food of adult?summer?.Tree sparrows from BY had higher AC values than those from LJX,indicating tree sparrows from BY will consume more heavy metals.6.Biomagnification of heavy metals from food to tree sparrows.With few exceptions,biomagnification factors?BMF values?were all above 1.0,indicating a biomagnification of heavy metals from food to tree sparrows exists.Lead concentrations were biomagnified by 2.29 to 7.08times with the most significant biomagnification.A significant linear relationship was found between heavy metal concentrations and?¹⁵N values of tree sparrows'food and primary feathers from LJX and BY?R2?0.3309,p<0.05?.Moreover,trophic magnification factors?TMF values?of heavy metals were all above 1.0,indicating a biomagnification of heavy metals as the trophic level increased is happened.In a word,Cu,Zn,Pb and Cd concentrations were found biomagnified from foods to tree sparrows from LJX and BY,and they increased with the trophic levels.7.Heavy metal intake levels of tree sparrows from LJX and BY.Nestlings had the highest heavy metal daily intake?MDI values?and heavy metal daily intake per unit of body weight(MDI_BW values)followed by adult?summer?.MDI and MDI_BW values of juveniles and adult?winter?were comparable.MDI and MDI_BW values of tree sparrows from BY were higher than those from LJX?p<0.05?,indicating heavy metal pollution can increase the exposure levels of heavy metals.Besides,different food sources had different contributions to MDI values.Invertebrates were found positively correlated with MDI values,while crops showed the opposite trend.All in all,heavy metal intake levels of tree sparrow nestlings,juveniles and adults from BY were higher than those from LJX,and nestlings had the highest intake levels among tree sparrows at different life stages.8.Exposure levels and risks of tree sparrows.Exposure level?EL value?,hazard quotient?HQ value?and hazard index?HI value?of tree sparrows via soil,water and food were calculated and found that nestlings had the highest values followed by adult?summer?,while juveniles and adult?winter?had the comparable values.For tree sparrow nestlings,juveniles and adults from both LJX and BY,HQ and HI values of Zn and Pb were above 3.0,indicating a high risk to tree sparrows.In addition,EL,HQ and HI values of BY were higher than those of LJX?p<0.05?.In a word,exposure levels and risks of tree sparrows from BY were higher than those from LJX and nestlings had high exposure risks.In conclusion,Cu,Zn,Pb and Cd concentrations of primary feathers,blood and faeces of tree sparrow from BY were higher than those from LJX,indicating they can be indicators for biological effects of long-term heavy metal pollution.Nestlings consumed invertebrates most,while juveniles and adults consumed crops and grass seeds most.Invertebrates had higher concentrations than crops and grass seeds,so nestlings had higher MDI values and exposure risks than juveniles and adults.Copper,Zn,Pb and Cd concentrations of soil,water and food from BY were higher than those from LJX.Higher exposure risks were found to tree sparrows from BY than those from LJX.In addition,there was an obvious biomagnification of heavy metals from food to tree sparrows,indicating there is a significant biomagnification effect of heavy metals from food to tree sparrows which aggravates the exposure risks of tree sparrows,even if they live in the habitats with low environmental heavy metal concentrations for a long time.